Summary PCL injuries are traumatic knee injuries that may lead to posterior knee instability and often present in combination with other ipsilateral ligamentous knee injuries (i.e PLC, ACL). Diagnosis can be suspected clinically with a traumatic knee effusion and increased laxity on a posterior drawer test but requires an MRI for confirmation. Treatment can be nonoperative or operative depending on the severity of injury to the PCL, as well concomitant injuries to surrounding structures and ligaments in the knee. Epidemiology Incidence 5-20% of all knee ligamentous injuries Etiology Pathophysiology mechanism direct blow to proximal tibia with a flexed knee (dashboard injury) noncontact hyperflexion with a plantar-flexed foot hyperextension injury pathoanatomy PCL is the primary restraint to posterior tibial translation functions to prevent hyperflexion/sliding isolated injuries cause the greatest instability at 90° of flexion Associated conditions combined PCL and posterolateral corner (PLC) injuries multiligamentous knee injuries knee dislocation Anatomy PCL anatomy origin anterolateral medial femoral condyle broad, crescent-shaped footprint insertion posterior tibial sulcus below the articular surface dimensions 38 mm in length x 13 mm in diameter PCL is 30% larger than the ACL PCL has two bundles anterolateral bundle tight in flexion strongest and most important for posterior stability at 90° of flexion mnemonic "PAL" - PCL has an AnteroLateral bundle posteromedial bundle tight in extension reciprocal function to the anterolateral bundle lies between the meniscofemoral ligaments ligament of Humphrey (anterior) and ligament of Wrisberg (posterior) originate from the posterior horn of the lateral meniscus and insert into PCL substance Blood supply supplied by branches of the middle geniculate artery and fat pad Biomechanics strength is 2500 to 3000 N (posterior) minimizes posterior tibial displacement (95%) Classification PCL injury classification (based on posterior subluxation of tibia relative to femoral condyles with knee in 90° of flexion) Grade I a partial tear exam shows 1-5 mm posterior tibial translation Tibia remains anterior to the femoral condyles Grade II a complete isolate tear exam shows 6-10 mm posterior tibial translation complete injury in which the anterior tibia is flush with the femoral condyles Grade III a combined PCL + capsuloligamentous injury exam shows >10mm posterior tibial translation tibia is posterior to the femoral condyles and often indicates an associated ACL and/or PLC injury Presentation History differentiate between high- and low-energy trauma dashboard injury hyperflexion athletic injury with a plantar-flexed foot ascertain a history of dislocation or neurologic injury Symptoms posterior knee pain instability often subtle or asymptomatic in isolated PCL injuries Physical exam varus/valgus stress laxity at 0° indicates MCL/LCL and PCL injury laxity at 30° alone indicates MCL/LCL injury posterior sag sign patient lies supine with hips and knees flexed to 90°, examiner supports ankles and observes for a posterior shift of the tibia as compared to the uninvolved knee the medial tibial plateau of a normal knee at rest is 10 mm anterior to the medial femoral condyle an absent or posteriorly-directed tibial step-off indicates a positive sign posterior drawer test (at 90° flexion) with the knee at 90° of flexion, a posteriorly-directed force is applied to the proximal tibia and posterior tibial translation is quantified isolated PCL injuries translate >10-12 mm in neutral rotation and 6-8 mm in internal rotation combined ligamentous injuries translate >15 mm in neutral rotation and >10 mm in internal rotation most accurate maneuver for diagnosing PCL injury quadriceps active test attempt to extend a knee flexed at 90° to elicit quadriceps contraction positive if anterior reduction of the tibia occurs relative to the femur dial test > 10° ER asymmetry at 30° & 90° consistent with PLC and PCL injury > 10° ER asymmetry at 30° only consistent with isolated PLC injury KT-1000 and KT-2000 knee ligament arthrometers used for standardized laxity measurement although less accurate than for ACL Imaging Radiographs recommended views AP and supine lateral may see avulsion fractures with acute injuries assess for posterior tibiofemoral subluxation medial and patellofemoral compartment arthrosis may be present with chronic injuries lateral stress view apply stress to anterior tibia with the knee flexed to 70° asymmetric posterior tibial displacement indicates PCL injury contralateral knee differences >12 mm on stress views suggest a combined PCL and PLC injury becoming the gold standard in diagnosing and quantifying PCL injuries kneeling stress radiographs of knee MRI confirmatory study for the diagnosis of PCL injury Treatment Nonoperative protected weight bearing & rehab indications isolated Grade I (partial) and II (complete isolated) injuries modalities quadriceps rehabilitation with a focus on knee extensor strengthening outcomes return to sports in 2-4 weeks relative immobilization in extension for 4 weeks indications isolated Grade III injuries surgery may be indicated with bony avulsions or a young athlete modalities extension bracing with limited daily ROM exercises immobilization is followed by quadriceps strengthening Operative PCL repair of bony avulsion fractures or reconstruction indications combined ligamentous injuries PCL + ACL or PLC injuries PCL + Grade III MCL or LCL injuries isolated Grade II or III injuries with bony avulsion isolated chronic PCL injuries with a functionally unstable knee techniques primary repair of bony avulsion fractures with ORIF reconstruction options include tibial inlay vs. transtibial methods single-bundle vs. double-bundle autograft vs. allograft allograft is typically utilized with multiple graft choices available options include - Achilles, bone-patellar tendon-bone, hamstring, and anterior tibialis outcomes good results achieved with primary repair of bony avulsions primary repair of midsubstance ruptures are typically not successful results of PCL reconstruction are less successful than with ACL reconstruction and residual posterior laxity often exists successful reconstruction depends on addressing concomitant ligament injuries no outcome studies clearly support one reconstruction technique over the other high tibial osteotomy indications chronic PCL deficiency techniques consider medial opening wedge osteotomy to treat both varus malalignment and PCL deficiency when performing a high tibial osteotomy in a PCL deficient knee, increasing the tibial slope helps reduce the posterior sag of the tibia shifts the tibia anterior relative to the femur preventing posterior tibial translation Surgical Techniques Arthroscopic transtibial technique approach standard arthroscopic portals with an accessory posteromedial portal posteromedial portal is placed 1 cm proximal to the joint line posterior to the MCL avoid injury to branches of the saphenous nerve during placement posteromedial corner of the knee is best visualized with a 70° arthroscope either through the notch (modified Gillquist view) or using a posteromedial portal technique transtibial drilling anterior to posterior fix graft in 90° flexion with an anterior drawer results in knee biomechanics similar to native knee pros & cons risk to popliteal vessels Open (tibial inlay) approach uses a posteromedial incision between medial head of gastrocnemius and semimembranosus technique used for ORIF of bony avulsion pros & cons biomechanical advantage with a decrease in the "killer turn" with less graft attenuation and failure screw fixation of the graft bone block is within 20 mm of the popliteal artery Single-bundle technique approach arthroscopic or open technique reconstruct the anterolateral bundle tension at 90° of flexion Double-bundle technique approach arthroscopic or open techniques may be utilized technique anterolateral bundle tensioned in 90° of flexion posteromedial bundle tensioned in extension pros & cons biomechanical advantage with knee function in flexion and extension clinical advantage has yet to be determined may be advantageous to perform with combined PCL/PLC injuries for better rotational control as PLC reconstructions typically loosen over time Rehabilitation Postoperative care immobilize in extension early and protect against gravity early motion should be in prone position Rehabilitation focus on quadriceps rehabilitation avoid resisted hamstring strengthening exercises (ex. hamstring curls) in early rehab this is because the hamstrings create a posterior pull on the tibia which increases stress on the graft. Complications Popliteal artery injury at risk when drilling the tibial tunnel (increases with knee extension) lies just posterior to PCL insertion on the tibia, separated only by posterior capsule Patellofemoral and medial sided pain/arthritis due to chronic PCL deficiency Prognosis Chronic PCL deficiency PCL deficiency leads to increased contact pressures in the patellofemoral and medial compartments of the knee due to varus alignment controversial whether late patellar and MFC chondrosis will develop